Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor, a combustor, and a turbine connected to a generator. The mechanical energy produced by the compressor, combustor and turbine is transferred to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The stator of a typical generator includes a plurality of stator bars. The stator bars are placed in slots defined in a core of the stator, and are held in place in the slots by various components. For example, a resilient member, such as a ripple spring, is place between a stator bar and a stator wedge in the slot. The stator wedge and resilient member secure the stator bar in place. The stator wedge is retained in the slot at a required preload tightness by the resilient member, to ensure that the stator bar remains securely in place.
In many cases, particularly during in situ maintenance of generators, the amount of preload that the stator wedges are being subjected to requires monitoring. For example, during operation of the generator, the stator wedge can creep and/or the resilient member can wear. This lessens the amount of preload, and can cause stator bars to loosen.
Currently known methods for testing stator wedge preload include, for example, stator wedge tapping. A stator wedge is tapped with, for example, a hammer. The resulting sound is evaluated, either audibly or using suitable software and hardware, and correlated to preload. For example, the frequency and/or vibrations of the resulting sound may be evaluated. However, correlation of these sounds to preload is tenuous. Further, specific preload measurements are not available, and the tests are not generally repeatable because the operator may tap the stator wedge in a different place or with a different force.
Accordingly, improved measurement systems and methods for measuring preload in generators are desired in the art. For example, measurement systems and methods that can provide specific, accurate, and repeatable preload measurements would be advantageous. Further, such measurement systems and methods that can be utilized in in situ applications would be desired.